This invention relates to the separation of hydrogen from a mixture of gases containing hydrogen by means of membrane separation combined with adsorption, or with cooling, and partial condensation and/or rectification and/or scrubbing.
A gaseous mixture containing hydrogen is obtained for example as a purge gas in ammonia or methanol synthesis. As the gaseous mixture contains valuable, reusable components, in particular hydrogen, argon and methanol, they are desirably recovered from the gaseous mixture and reused. Furthermore, components detrimental to such reuse are separated from the mixture of gases.
If only hydrogen is to be recovered, the rest of the components of the gaseous mixture is separated by condensation and/or adsorption from the hydrogen. If, on the other hand, other components are also to be recovered, the gaseous mixture is passed to one or several separating stages, in which the individual components are separated by partial condensation and/or rectification and/or scrubbing and withdrawn as overhead or bottoms, depending on their physical properties. The operation of the process usually requires external refrigeration, supplied by a high pressure refrigerating circuit, for example a nitrogen cycle.
Disadvantageous to this process is that substantial amounts of energy must be provided to generate the necessary low temperatures and/or the separated gaseous products can be obtained only at a relatively low pressure. Furthermore, a high pressure refrigeration cycle necessarily involves large expenditures for equipment, e.g., compressors, condenser, conduits and fittings.